This invention relates to improvements in patient transfer apparatus and more particularly, it concerns an improved upper belt and separator assembly especially suited for use in patient transfer mechanisms of the type disclosed in the aforementioned concurrently filed and co-pending application of Laurel A. Koll.
In U.S. Pat. No. 3,493,979 issued Feb. 10, 1970 to Laurel A. Koll and Walter Crook, Jr., there is disclosed an object transfer method and apparatus by which a pair of superimposed endless belts, trained about plate-like separators or supports, are translated from a retracted position on the deck structure of a litter-like chassis outwardly over a bed or other surface on which an object or patient is initially reclined in a manner such that relative rotation of the endless belts with respect to the separators causes the upper belt flight on the upper separator and the lower belt flight on the lower separator to remain stationary relative to the chassis. These belt flights insulate sliding friction between the separators and the patient, on the one hand, and the separators and the bed or other surface on the other hand as the assembly of the separators and endless belts are translated between the patient and the bed surface until the object or patient overlies the separator. To transfer the patient back onto the litter-like chassis of the transfer apparatus, the lower belt is rotated in a reverse direction relative to its separator while the upper belt is retained against rotation about its support and thus moves as a unit with the upper support to translate the patient in the direction of separator retraction. Hence, both endless belts serve as friction isolating aprons during loading translation of the separator but the upper belt or apron may be conditioned also to transmit frictional forces between the upper support and object or patient when movement of the latter with the support is called for.
Further developments of the basic apparatus disclosed in the aforementioned U.S. patents are found in U.S. Pat. No. 3,579,672 issued May 25, 1971 to Laurel A. Koll and Walter Crook, Jr.; U.S. Pat. No. 3,765,037 issued Oct. 16, 1973 to Albert Dunkin; and more recently, in the aforementioned co-pending application. The disclosure in U.S. Pat. No. 3,579,672 represents a significant improvement over the basic apparatus disclosed in the first-mentioned patent, principally in its recognition that the concept could be applied to very thin, flexible separator plates and by the use of paper-thin teflon-coated fiberglass or nylon belts so that the entire assembly which advanced beneath a patient would be both flexible and extremely thin; that is, on the order of 12 mm. or less. In addition, the belt establishing the upper apron, though endless, was trained through a flight path configuration about the lower separator principally to facilitate more precise control over movement in the flight portions of the endless belt extending about the top, front endge and bottom surfaces of the upper separator. Movement of the lower apron or endless belt, in the disclosure of this patent, is controlled precisely by fixing a portion of the lower flight portion of the lower apron to a front edge of the chassis deck.
In U.S. Pat. No. 3,765,037, the drive organization for the upper belt or apron was improved to provide more positive control over movement of the respective operative belt flight portions and also to facilitate the incorporation of a belt tracking mechanism. In this latter respect, the separators in all of the respective transfer apparatus referred to are on the order of 60 cm. in width and on the order of 180 cm. in length complement the size of a normal patient. The belts forming the aprons being movable transversely or about the narrow dimension of the separators, are thus extremely wide. Although tracking of the lower belt was of no consequence in either of the latter disclosures because it was fixed along its lower flight portion to the chassis deck, the upper belt was much longer than the width of the separators in order to facilitate flight portions cooperating with the drive mechanism. As a result, a tracking mechanism was needed to retain the upper belt centered longitudinally of the separator.
In the aforementioned concurrently filed co-pending application, the upper apron is again formed by a simple endless belt trained about the width of the upper separator and either driven relative to the separator by a drive roller positioned along the rear edge of the separator, or retained against movement relative to the upper separator by non-rotation of the roller. Because of the relatively small diameter of the roller to accommodate the thin plate-like nature of the separator, provision must be made for tensioning the upper belt or apron on the upper separator. In addition, the extreme width of the belt (approximating the length of the separator and thus of a normal person) makes it difficult to assure complete parellelism of the endless belt flights during manufacture. Accordingly, provision must be made for adjusting angular relation of the front edge of the separator with respect to the drive roller so that a given belt will track properly on the separator.